[coolspot]

Not in the compiler but in GPU driver. A graphic program (or compute) just calls APIs (DirectX/Vulkan/CUDA) of a driver, which then knows how to do that on a low-level writing to particular regions of RAM mapped to GPU registers.

[danielmarkbruce]

Yes! This is correct. My bad, it's been too long. I guess either way the point is that it's done in software, not hardware.

[lxgr]

There's also odd/interesting architectures like one of the earlier Raspberry Pis, where the GPU was actually running its own operating system that would take care of things like shader compilation.

In that case, what's actually being written to shared/mapped memory is very high level instructions that are then compiled or interpreted on the GPU (which is really an entire computer, CPU and all) itself.